Electrical Performance Prediction Based On Structural Measurements Of Partially Fabricated Semiconductor Devices

Abstract

Methods and systems for measurement of an expected electrical performance of a semiconductor device after device formation is complete based on structural measurements of the device in a partially fabricated state are described herein. In a further aspect, process parameters associated with a process step are adjusted based on the predicted electrical performance to improve process yield. In this manner, process parameters are tuned without having to wait several weeks for electrical performance test measurements to occur at the end of a process flow. In preferred embodiments, a Multiple Reflection Spectroscopic Ellipsometry (MRSE) system is employed to perform structural measurements of a semiconductor device in a partially fabricated state to predict electrical performance of the device at the end of the device fabrication process flow. MRSE based measurements are performed at one or more critical process steps where the structural measurements correlate strongly with final electrical performance.

What is claimed is: 
     
         1 . A measurement system comprising:
 an illumination source configured to generate a first amount of illumination light directed to a first measurement site on a surface of a semiconductor wafer during a first measurement instance, the semiconductor wafer processed through a first process step of a plurality of process steps of a semiconductor fabrication process flow from bare wafer to an electrical interconnect metallization process step, wherein a first instance of one or more structures under measurement is located at the first measurement site;   at least one detector having a planar, two-dimensional surface sensitive to incident light, the at least one detector configured to detect a first amount of light collected from the surface of the semiconductor wafer in response to the first amount of illumination light and generate a first set of output signals indicative of the detected light during the first measurement instance; and   a computing system configured to determine an estimated value of an electrical performance metric based at least in part on the first set of output signals, the estimated value of the electrical performance metric indicative of an expected electrical performance of a semiconductor device including the one or more structures under measurement as if the semiconductor wafer were processed through the plurality of process steps of the semiconductor fabrication process flow.   
     
     
         2 . The measurement system of  claim 1 , the illumination source further configured to generate a second amount of illumination light directed to the first measurement site on the surface of the semiconductor wafer during a second measurement instance, the semiconductor wafer processed through a second process step of the plurality of process steps, the at least one detector further configured to detect a second amount of light collected from the surface of the semiconductor wafer in response to the second amount of illumination light and generate a second set of output signals indicative of the detected light during the second measurement instance, wherein the determining of the estimated value of the electrical performance metric is based at least in part on the first and second sets of output signals. 
     
     
         3 . The measurement system of  claim 1 , the computing system further configured to:
 determine an updated value of one or more process parameters characterizing the first process step, a process step of the plurality of process steps prior to the first process step, a process step subsequent to the first process step of the plurality of process steps, or any combination thereof, based on the estimated value of the electrical performance metric.   
     
     
         4 . The measurement system of  claim 1 , the computing system further configured to:
 estimate values of one or more parameters of interest characterizing one or more structural features of the one or more structures under measurement based at least in part on the first set of output signals, wherein the determining of the estimated value of the electrical performance metric is based at least in part on the estimated values of the parameters of interest.   
     
     
         5 . The measurement system of  claim 4 , the computing system further configured to:
 determine an updated value of one or more process parameters characterizing the first process step, a process step of the plurality of process steps prior to the first process step, a process step subsequent to the first process step of the plurality of process steps, or any combination thereof, based on the estimated value of the electrical performance metric and the estimated values of the one or more parameters of interest.   
     
     
         6 . The measurement system of  claim 1 , wherein the semiconductor device is a logic device, and wherein the electrical performance metric is any of a drive current, a threshold voltage, a carrier mobility, a current leakage, and a breakdown voltage. 
     
     
         7 . The measurement system of  claim 1 , wherein the semiconductor device is a memory device, and wherein the electrical performance metric is any of a capacitance, a read and write speed, and a reliability. 
     
     
         8 . The measurement system of  claim 1 , wherein the semiconductor device is a gate-all-around transistor. 
     
     
         9 . The measurement system of  claim 1 , wherein the one or more structures under measurement are fabricated in-die. 
     
     
         10 . The measurement system of  claim 1 , wherein the illumination source, the at least one detector, and the computing system comprise a Multiple Pass Spectroscopic Ellipsometry (MPSE) metrology system. 
     
     
         11 . The measurement system of  claim 10 , further comprising:
 one or more reflective optical elements disposed in an optical path between the illumination source and the at least one detector, wherein the optical path is incident on the surface of the semiconductor wafer more than once.   
     
     
         12 . The measurement system of  claim 11 , the one or more reflective optical elements including at least two reflective optical elements, the at least two reflective optical elements positioned in the optical path to direct light from the first measurement site back to the first measurement site. 
     
     
         13 . The measurement system of  claim 11 , the one or more reflective optical elements including a planar reflector having a planar reflective surface disposed over the wafer and facing the wafer surface, wherein the planar reflector is positioned in the optical path to direct light from the first measurement site to a second measurement site on the surface of the semiconductor wafer, wherein a second instance of the one or more structures under measurement is located at the second measurement site. 
     
     
         14 . The measurement system of  claim 10 , further comprising:
 a second metrology system configured to generate a second set of output signals indicative of a measurement of the one or more structures under measurement, wherein the determining of the estimated value of the electrical performance metric is based on the first and second sets of output signals.   
     
     
         15 . The measurement system of  claim 14 , wherein the second metrology system is a spectroscopic reflectometer, an angle resolved reflectometer, a x-ray diffractometer, or a raman spectrometer. 
     
     
         16 . A method comprising:
 generating a first amount of illumination light by an illumination source;   directing the first amount of illumination light to a first measurement site on a surface of a semiconductor wafer during a first measurement instance, the semiconductor wafer processed through a first process step of a plurality of process steps of a semiconductor fabrication process flow from bare wafer to an electrical interconnect metallization process step, wherein a first instance of one or more structures under measurement is located at the first measurement site;   detecting a first amount of light collected from the surface of the semiconductor wafer in response to the first amount of illumination light;   generating a first set of output signals indicative of the detected light during the first measurement instance; and   determining an estimated value of an electrical performance metric based at least in part on the first set of output signals, the estimated value of the electrical performance metric indicative of an expected electrical performance of a semiconductor device including the one or more structures under measurement as if the semiconductor wafer were processed through the plurality of process steps of the semiconductor fabrication process flow.   
     
     
         17 . The method of  claim 16 , further comprising:
 generating a second amount of illumination light directed to the first measurement site on the surface of the semiconductor wafer during a second measurement instance, the semiconductor wafer processed through a second process step of the plurality of process steps;   detecting a second amount of light collected from the surface of the semiconductor wafer in response to the second amount of illumination light;   generating a second set of output signals indicative of the detected light during the second measurement instance, wherein the determining of the estimated value of the electrical performance metric is based at least in part on the first and second sets of output signals.   
     
     
         18 . The method of  claim 16 , further comprising:
 determining an updated value of one or more process parameters characterizing the first process step, a process step of the plurality of process steps prior to the first process step, a process step subsequent to the first process step of the plurality of process steps, or any combination thereof, based on the estimated value of the electrical performance metric.   
     
     
         19 . The method of  claim 16 , further comprising:
 estimating values of one or more parameters of interest characterizing one or more structural features of the one or more structures under measurement based at least in part on the first set of output signals, wherein the determining of the estimated value of the electrical performance metric is based at least in part on the estimated values of the parameters of interest.   
     
     
         20 . The method of  claim 19 , further comprising:
 determining an updated value of one or more process parameters characterizing the first process step, a process step of the plurality of process steps prior to the first process step, a process step subsequent to the first process step of the plurality of process steps, or any combination thereof, based on the estimated value of the electrical performance metric and the estimated values of the one or more parameters of interest.   
     
     
         21 . A measurement system comprising:
 an illumination source configured to generate a first amount of illumination light directed to a first measurement site on a surface of a semiconductor wafer during a first measurement instance, the semiconductor wafer processed through a first process step of a plurality of process steps of a semiconductor fabrication process flow from bare wafer to an electrical interconnect metallization process step, wherein a first instance of one or more structures under measurement is located at the first measurement site;   at least one detector having a planar, two-dimensional surface sensitive to incident light, the at least one detector configured to detect a first amount of light collected from the surface of the semiconductor wafer in response to the first amount of illumination light and generate a first set of output signals indicative of the detected light during the first measurement instance; and   a non-transitory, computer-readable medium storing instructions that, when executed by one or more processors, causes the one or more processors to:   determine an estimated value of an electrical performance metric based at least in part on the first set of output signals, the estimated value of the electrical performance metric indicative of an expected electrical performance of a semiconductor device including the one or more structures under measurement as if the semiconductor wafer were processed through the plurality of process steps of the semiconductor fabrication process flow.